interface. In a high level there are a 
management program for the transıt of 
informations between both: So, for 
example, to associate a data {from the 
graphic Tile to the literal file, is 
necessary to create a text file from the 
graphics file which is read by the 
management program and related with his 
homologous in the literal file. The same 
Process is used for inverse case. 
The relationship between the two types of 
information is usually executed through 
geocodes. This process is usefull due his 
implementation facility, but has, as 
disavantage the time necessary to execute 
the process. This problem can be decrease 
if we use binary code for the transit of 
information. 
4.2 Interface Language 
Another interface possibility between the 
two informations is through the direct 
relationship between its structures. To do 
this, others information are added in the 
literal or graphic file, in order to store 
the address of his homologous in the other 
structure. 
For example, lets take the case when the 
relation structure is together with the 
graphic information. The management 
program must access this structure and 
through it execute the relationship 
between both, in one of following ways: 
E after identifying the graphic 
element, the management program reads the 
literal information addresses and accesses 
the correspondent entity through the query 
language; 
- choose one literal record, the 
management Program, through pointers 
sgstem, identify the especific graphic 
information. 
This process has been used in some systems 
mainly because they don't need a very hard 
development and utilizes the graphic and 
literal structures already available. As 
disavantage we have the difficult for 
updating due to the fact the information 
are related to one object in two 
differents places. 
4.3 Relational Model Extent 
The relational model represents a database 
descrition through simple and well known 
mathematics concepts. Its goal is to allow 
the user to visualize the database as a 
set of tables where each line represents a 
record and its attributes. 
The 1NF (First Normal Form) is important 
for the database implementation, therefore 
when using complex objects this form must 
be out, considering the characteristics of 
those objects. So, the relation has as 
attributes one n-uple of objects or a set 
of objects. Among others, we will 
introduce three possibilities for 
applicating the relational model to 
complex objects. 
482 
4.3.1 Relational hierarchal structures 
Each complex object is represented by 
one or more relations. This way, the chain 
is made from the root row to the rows 
hierarchal dependent, creating one strong 
relationship between the table. 
The problem with this idea is that due 
to the global dependency created between 
the table, when we take out one n-upla 
from it, we need to take out also the data 
for all the others tables. 
4.3.2 Ihe use of Abstract Data Tune — 
ADI 
The abstract data type is characterized 
as: 
- by definition of one set of objects, 
using one or more type definition; 
- by definition of one set of operators 
applicable to the objects; 
- by the encapsulate of the objects in 
a way that one normal user only sees it 
through defined operators. 
By ADT the designer can better defined 
as the set of operators for its 
application beyond, of promove the 
modularity in relation of the system 
changes. 
As a tool for complex objects 
representations, the ADT has the folowing 
approach: 
- use of the relation or domain as ADT 
allowing the freedom of data as well the 
abstration of the operation to one level; 
- only use the domains as ADT, where 
the objects must stay all the time in the 
memory. In this case one can use a host 
language, self-contained or other 
specifically developed for it; 
- use of hierarchy of types through the 
relationship between types and sub-types. 
4.3.3 [he relational algebra 
; Li : 
The relational operator in the 
convencional relational algebra only are 
efficients when used with common data 
type. When using complex objects, one new 
set of operators must be created to attend 
its peculiarity, either through the 
increase of its operationals 
characteristics or by the definition of 
other operators. 
4.4 Object-Oriented 
This representation is the most recent and 
has been of great attention to the 
researchers. 
The convencional systems needs the entity 
decomposition in elements simpler than 
considering that they are record oriented. 
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